1. Field of the Invention
The present invention relates to an art of a laser microscope, and especially to an art of a laser microscope using a phase-modulation type spatial light modulator.
2. Description of the Related Art
A technique to control the spatial distribution and intensity (hereinafter, referred to as a pattern) of light as needed and to apply light of a desired pattern on an object using a spatial light modulator (SLM) having a plurality of optical modulation elements (hereinafter, referred to as pixel elements) that are controlled independently from each other has been known.
While various kinds of SLMs have been proposed so far, an SLM in which pixel elements modulate the intensity of light (hereinafter, referred to as an intensity-modulation type SLM) as represented by Digital Micromirror Device (DMD) and an SLM in which pixel elements modulate the phase of light (hereinafter, referred to as a phase-modulation type SLM) has become popular.
An intensity-modulation type SLM is capable of applying light of a desired pattern by directly projecting the pattern of the intensity of light formed on the intensity-modulation type SLM on an object. However, for an intensity-modulation type SLM, a problem has been pointed out that since the pattern of the intensity of light is formed by eliminating incoming light selectively by the pixel elements, the light use intensity is low, and the density of the light applied on the object is also low.
By contrast, a phase-modulation type SLM changes the wavefront form of incoming light by phase modulation using a coherent light source such as a laser light source. This makes it possible to change the intensity distribution of light on an object and to form light of a desired pattern. In a phase-modulation type SLM, a desired pattern is formed by changing the phase distribution of light, little loss of light occurs in principle. For this reason, a higher light use efficiency can be achieved compared with an intensity-modulation type SLM. Japanese Laid-open Patent Publication 2006-72280 discloses a pattern formation apparatus and an optical tweezers apparatus using a phase-modulation type SLM.
Such a phase-modulation type SLM capable of applying light of a given pattern on an object with a high light density by suppressing loss of light and achieving a high light use efficiency has been applied to the field of laser microscopes such as a fluorescent microscope. In particular, application to a fluorescent microscope using nonlinear optical phenomena that requires a very high light density is effective, and Volodymyr Nikolenko and five others, “SLM microscope: scanless two-photon imaging and photostimulation with spatial light modulators”, Frontiers in Neural Circuits, 19 Dec. 2008, Volume 2, Article 5, p. 1-14 (hereinafter, referred to as non-patent document 1) discloses a two-photon excitation microscope being a type of nonlinear microscopes.
The microscope disclosed in non-patent document 1 is capable of applying light of a given pattern (hereinafter, referred to as light pattern application) on an object while suppressing loss of light by using a phase-modulation type SLM. For this reason, light with a high light density required for generating a nonlinear phenomenon can be applied on a plurality of parts of an object simultaneously without scanning the object.
Incidentally, with fluorescent observation using a fluorescent microscope, there is need to observe dynamic changes of an object (including dynamic change of a fluorescent material included in an object) that occur with the light pattern application, such as photoactivation, photoconversion, FRAP (Fluorescence Recovery After Photobleaching), FLIP (Fluorescence Loss In Photobleaching) and so on. In order to meet the need, a function for imaging a given area of an object aside from a light pattern application area is needed.
Meanwhile, such need to observe dynamic changes of an object is present not only with fluorescent microscopes but also with other laser microscopes.
The microscope disclosed in the non-patent document 1 has a galvanometer scanner as scanning means. For this reason, it can be used also as a normal laser scanning microscope (hereinafter, referred to as LSM), and is capable of imaging a given area of an object.
Meanwhile, in the microscope disclosed in the non-patent document 1, the phase-modulation type SLM for the light pattern application and the scanning means for imaging of the object are placed on the same light path.